I generally don't. But I have before.
At the park. All toilets closed because it was like 5 pm and he needed to go. Was my only choice.
And just the other day. He was busting and someone was in the bathroom so he went out the front.
Though there has been a few times when he has gone out the back without my knowledge! So not much I can do there I suppose. I just tell him he should be using the toilet in the bathroom and not going outside!
He is 4
What I did see just recently at the shopping centre. Guy at the taxi stand with a boy and girl. She would've been about 6-7. And she needed to go to the toilet. He put her up near the bushy area and let her pee there. When there was toilets a few meters away inside! That was a little weird.